Research ArticlePre-Reducing Process Kinetics to Recover Metals from NickelLeach Waste Using Chelating Resins

Amilton Barbosa Botelho Junior ,1 David Bruce Dreisinger,2

Denise Crocce Romano Espinosa,1 and Jorge Alberto Soares Tenorio1

1Department of Chemical Engineering, Polytechnic School of University of São Paulo, Sao Paulo, Brazil2Department of Materials Engineering, "e University of British Columbia, Vancouver, Canada

Correspondence should be addressed to Amilton Barbosa Botelho Junior; amilton.barbosa20@gmail.com

Received 12 June 2018; Revised 12 July 2018; Accepted 30 July 2018; Published 9 October 2018

Academic Editor: Eric Guibal

Copyright © 2018 Amilton Barbosa Botelho Junior et al. %is is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in anymedium, provided the original work isproperly cited.

%e main problem of the separation process from nickel mining using the ion exchange technique is the presence of iron, whichprecipitates in pH above 2.00 and causes coprecipitation of copper and cobalt. Chelating resins have the main advantage of beingselected for a specific metal present in solution. Studies have been developed to increase the efficiency of metals recovery usingchemical reduction and the ion exchange process to recover metals. %e aim of this work was to use sodium sulfite as a reducingagent to convert Fe(III) to Fe(II). Chelating resins Lewatit® TP 207, selective for copper, and Lewatit® TP 220, selective for nickeland cobalt, were studied. Batch experiments were performed to study the effect of pH with and without sodium sulfite. Resultsindicated that the industrial process has increased efficiency when the reducing process is applied.

1. Introduction

Nickel laterite represents 70% of nickel reserves and 40% ofnickel production, mostly processed by the hydrometal-lurgical process, due to the fact that the nickel lateriteprocess is more expensive and difficult than other ores [1–6].%e main problem for metals recovery, such as nickel,copper, and cobalt, from these ores is the high concentrationof iron. Limonite layer, the first layer of the nickel laterite oreand processed by high-pressure acid leaching or atmo-spheric acid leaching using sulfuric acid, has 40–50% of ironapproximately, while nickel concentration is 0.8–1.5% andcobalt concentration is 0.1–0.2% [7].

In order to separate iron from nickel laterite leach,Jimenez Correae et al. studied chemical precipitation of Fe(III) and Fe(II) in a solution of nickel laterite using hy-droxides. Results obtained show that, at pH 2.50, 30% of ironand 20% of cobalt precipitate. At pH 3.00, 100% of iron, 60%of cobalt, and 20% of copper precipitate [8]. Another studyrealized by Chang et al. performed experiments to pre-cipitate iron from nickel laterite leach by the oxidation

process. Results show that there was loss of nickel to theresidue with all iron. Nickel can be recovered from theresidue using the weak acid solution, but more steps can turnthe process impracticable [9].

Ion exchange process using chelating resins can bea solution to selectively recover metals. For this reason,Jimenez Correa et al. studied copper and nickel recoveryusing the chelating resin Dowex M4195 from nickel lateriteleach waste. %e chelating resin has the bis-picolylaminefunctional group, and results show that copper recovery washighly influenced by iron due to its high concentration(150mg·L−1 of copper and 18000mg·L−1 of iron) [10]. Lit-tlejohn and Vaughan [11] studied nickel and cobalt recoveryusing the chelating resin Lewatit® TP 220, with the samefunctional group of M4195, from nickel laterite tailings.Ferric iron was the most significant impurity adsorbed byresin, and results were obtained by Jimenez Correa et al. [10].

Zainol and Nicol studied five chelating resins with theiminodiacetate functional group to recover nickel and cobaltfrom nickel laterite leach tailings. %e presence of iron, aswell as chromium and aluminum, decreased resins

HindawiInternational Journal of Chemical EngineeringVolume 2018, Article ID 9161323, 7 pageshttps://doi.org/10.1155/2018/9161323

efficiency, due to strong adsorption of these functionalgroups. In spite of all resins studied having the samefunctional group, results were different, and TP 207 Mon-oPlus had better results for nickel recovery [12]. Comparingmetals recovery using Lewatit® TP 207 with the imino-diacetate functional group, copper recovery is higher thannickel in all pH values studied by Rudnicki et al. [13]. Metalsrecovery, both copper and nickel, increased when pH in-creases [13].

According to Littlejohn and Vaughan and Mendes andMartins, chelating resins with the iminodiacetate functionalgroup are better to recover copper, and resins with the bis-picolylamine functional group were more selective for nickeland cobalt than the others metals [14, 15].

In spite of chelating resins used to selectively recovermetals, iron still is a problem to overcome. Botelho Junioret al. studied the difference between ferric iron and ferrousiron in nickel laterite leach waste for copper recovery usingLewatit® TP 207, in which chelating resin efficiency in-creases when iron is present as ferrous iron. In solution withFe(III), copper recovery was 48.72%, while solution with Fe(II) copper recovery was 61.32% [16–18]. A way to convertferric iron to ferrous iron is using a reducing agent. Sodiumdithionite and sodium metabisulfite were studied to convertferric iron to ferrous iron of nickel laterite leach waste re-ducing the potential of the solution until 590mV (pH0.50–2.00) and 240mV (pH 2.50–3.50). However, theproblem is these reducing agents are dangerous in acidsolutions, which can release hydrogen sulfide (H2S), andthese reducing agents can be added if dissolved in waterbefore. %e other problem is they are expensive [19–21].

Other reducing agents that can be used such as sodiumthiosulfate or microorganismos have the same problem inacid solutions [22–26]. Nevertheless, sodium sulfite is a re-ducing agent that can be used in acid solutions. Liu et al.studied reductive stripping of ferric iron using sulfuric acidand sodium sulfite [27]. Luo et al. studied atmosphericleaching of nickel limonite with sulfuric acid using sodiumsulfite as a reducing agent to facilitate nickel extraction,comparing the leaching process using only sulfuric acid.Results indicated that nickel extraction increases in presenceof sodium sulfite, as well as iron extraction. %ough thenickel extraction increased, the increase of the iron ex-traction still keeps the problem [28].

%e goal of this work was to study the batch industrialprocess to recover copper, nickel, and cobalt using the ionexchange technique. Chelating resins Lewatit® TP 207, se-lective for copper with the iminodiacetate functional group,and Lewatit® TP 220, selective for nickel and cobalt with bis-picolylamine functional group, were studied. Sodium sulfitewas used to reduce the potential of solution, convertingferric iron to ferrous iron, while the reducing process wasstudied before using sodium dithionite and sodium meta-bisulfite [19, 20, 29].%ree synthetic solutions were preparedto simulate real conditions of nickel laterite leach waste fromthe limonite ore. Solution 1 was used to study copper re-covery, Solution 2 without copper was used to study nickelrecovery; and Solution 3 without copper and nickel was usedto study cobalt recovery. Effect of pH was studied between

pH 0.50 and 2.00, for solutions without sodium sulfite, andbetween pH 0.50 and 3.50, with sodium sulfite. Experimentswere performed in a batch at 25°C and 150 rpm. Sampleswere analyzed using ICP-OES (Varian 725ES).

2. Materials and Methods

2.1. Materials. Composition of synthetics solutions ispresent in Table 1. Sulfate salts of each metal were dissolvedin deionized water, and the pH was adjusted with sulfuricacid concentrated PA. %ree different solutions were pre-pared: Solution 1 was prepared with all metals that composethe nickel laterite leach, Solution 2 was prepared withoutcopper, and Solution 3 was prepared without copper andnickel. %erefore, it is a possible study effect of other metalspresented in the leach solution for copper, nickel, and cobaltadsorption in three steps.

Two different chelating resins were studied: Lewatit® TP207, for experiments performed using Solution 1, andLewatit® TP 220, for experiments performed using Solutions2 and 3. TP 207 is a cationic resin with the iminodiacetatefunctional group, crosslinked polystyrene macroporousmatrix, pH range 0–14 and density 1.17g·mL−1 [30]. %etheoretical selectivity order for this resin is Fe(III)>Cu(II)>Ni(II)>Zn(II)> Fe(II)>Mn(II)>Mg(II) [13]. TP 220 isalso a cationic resin, but with the bis-picolylamine functionalgroup, crosslinked polystyrene macroporous matrix, density1.1g·mL−1. %e theoretical selectivity order for this resin isCu(II)>Ni(II)> Fe(III)>Co(II)>Mn(II)>K(I)>Ca(II)>Na(I)>Mg(II)>Al(III) [11, 31].

2.2. Method

2.2.1. Pre-Reducing Process. Botelho Junior et.al. studied thereducing process using sodium dithionite and sodiummetabisulfite to convert Fe(III) to Fe(II) from the syntheticsolution of nickel laterite leach. Effect of time, pH, andtemperature was studied. Temperature decreased ferric ironchemical conversion, probably due to the reducing agentcomposition. %e effect of time was studied until 96 hours,and after 120min, the reaction reaches equilibrium, until480min, and then decreased from 95% to 80% after1144min. Conversion of Fe(III) to Fe(II) in 100% wasperformed decreasing the potential until 590mV, at pH0.50–2.00, and 240mV, at pH 2.50–3.50. For synthetic so-lution with all metals of nickel laterite leach, ferric ironconversion is 80% [19, 20, 29].

%us, the pre-reducing process was performed during120min adding sodium sulfite in order to decrease thepotential until 590mV SHE (standard hydrogen electrode),pH 0.50–2.00, and 240mV SHE, pH 2.50–3.50, at 25°C in150 rpm.

2.2.2. Ion Exchange Experiments. Ion exchange experimentswere performed in flasks of 100mL with 50mL of solutionand 0.50mL of resin in 150 rpm at 25°C during 120min.%eeffect of time was studied without the pre-reducing processbetween 30 and 480min at pH 0.50 for Solution 1, with

2 International Journal of Chemical Engineering

Lewatit® TP 207, and Solution 2, with Lewatit® TP 220. eeect of pH was studied between pH 0.50 and 3.50.

Resins were washed using hydrochloric acid 6mol·L−1and sodium hydroxide 1mol·L−1 for three times using waterdeionized between each step. Sulfuric acid 1mol·L−1 wasused after wash. Sulfuric acid concentrated PA and sodiumhydroxide pellet were used to correct the pH [32].

In order to quantify the cations adsorbed, Equation (1)was used, where qt is the capacity of the ion adsorbed in timet in mass of the ion per mass of resin (mg·g−1), C0 · e · Ct areconcentrations of ions in time� 0 and time� t (mg·L−1), v isthe volume of solution (L), andm is the mass of the resin (g)[13, 33]. Equation (2) was used to quantify the coe�cient ofdistribution of ion, which one is the measure of the eec-tiveness of ion adsorption from solution [32]. Equation (3)was used to quantify the adsorbed ion, in percentage:

qt � C0 −Ct( ) ×v

m, (1)

Kd �qeCt

× 1000, (2)

%S �C0 −Ct( )C0

× 100%. (3)

e pH was measured using electrode Ag/AgCl (Sen-soglass), and electrode ORP (oxidation reduction potential)was used to measure the potential in solution. Samples wereanalyzed using ICP-EOS (Varian 725ES Optical EmissionSpectrometer).

3. Results and Discussion

Figure 1 presents Pourbaix’s diagram constructed usingHydra-Medusa software in experimental conditions for theFe-S-H2O system, where the conversion of Fe(III) to Fe(II) is100% after 590mV between pH 0.50 and 2.00, and it is after240mV between pH 2.50 and 3.50. However, presence ofthe other metals decreases the reducing process e�ciency.In acid medium with sulfuric acid, sodium sul�te reactswith H+ to form H2SO3, as presented in Equation (4), inwhich k1� 1.54×10−2 and k2�1.02×10−7. Besides, sodiumdithionite and sodium sul�te are dierent, and both dissociateto form sodium bisul�te, which is themain responsible for thereducing process in solution, but sodium dithionite alsodissociates to form sodium thiosulfate [27, 34–37].

SO2(aq) +H2⇌H+ +HSO−3 ⇌H+ + SO−23 (4)

Another problem about sodium dithionite is that acidmedium can be dissociated to form sulphur and hydrogensul�de, being the last extremely dangerous [38]. Besides,

sodium dithionite, sodium thiosulfate, and sodium bisulfateare dangerous because of same problem in the acid medium,using them only in the basic medium [23, 39].

3.1. E�ect of Time. e eect of time was studied usingSolution 1 and Solution 2 without the pre-reducing processat 25°C and pH 0.50. Results for copper (Solution 1) andnickel (Solution 2) recovery are present in Figure 2 andindicate that the reaction reached equilibrium after 120min,in which Solution 1 was in contact of Lewatit® TP 207 andSolution 2 with Lewatit® TP 220. Iron was the metal highestadsorbed in mg per g of resin (151mg·g−1), while copper was1.67mg·g−1, due to high concentration of H+ in solution atpH 0.50. For Solution 2, iron was also in this case the highestmetal adsorbed (85mg·g−1), while nickel was 10.87mg·g−1.Experiments to study the eect of pH in the ion exchangeprocess were performed during 120min.

3.2. E�ect of pH. e eect of pH in chelating resin with theiminodiacetate functional group can be seen in Figure 3. AtpH 2, high concentration of H+ in the functional grouprepulses cations in solution due to protonation of thefunctional group, where high competition between H+ andcations occurs by the functional group. At pH 2–4, H+ andcations present in the solution still compete for the chelatingresin functional group, the latter being deprotonated. InFigure 3, at pH 7, carboxylic acid of the functional group isdeprotonated, and at pH 12, the iminodiacetate functionalgroup is totally deprotonated. However, although the lastsituation is the most favorable to recover cations due to nopresence of H+ in the functional group, metals in general

Table 1: Metals concentration for batch experiments for Solution 1, Solution 2, and Solution 3 in mg·L−1.

Metals— Al Co Cu Cr Fe Mg Mn Ni Zn

Conc. (mg.L−1)Solution 1 4101 78 146 195 18713 7774 387 2434 36Solution 2 4101 78 — 195 18713 7774 387 2434 36Solution 3 4101 78 — 195 18713 7774 387 — 36

FeSO4+

FeHSO4+

FeSO4

FeS2(s)

Fe2O3(cr)0.8

0.6

590mV

240mV

E SH

E (V

)

0.4

0.2

0.00 1 2

pH3 4

FeHSO42+

Figure 1: Pourbaix’s diagram of Fe-S-H2O constructed usingHydra-Medusa software at 25°C.

International Journal of Chemical Engineering 3

precipitate at pH 5, which causes working pH to be totallydependent of solution characteristics [12, 13, 40].

Results for metals recovery with and without the pre-reducing process are present below. Eect of pH without thepre-reducing process above pH 2.00 was not studied, be-cause from this pH, iron will precipitate with copper andcobalt [8, 41]. Figure 4 presents results for copper recovery inSolution 1 by the iminodiacetate resin Lewatit® TP 207. It isobserved that copper recovery increased for Solution 1 withthe pre-reducing process. At pH 0.50, copper recovery was9.66% without the pre-reducing process, while using sodiumsul�te to convert Fe(III) to Fe(II), copper recovery at pH 0.50was 16.67%. At pH 2.00, both had highest copper recovery.In solution without sodium sul�te, copper recovery was41.43%, and with sodium sul�te as a reducing agent, copperrecovery was 68.57%.

Botelho Junior et al. studied the eect of presence of Fe(III) and Fe(II) to recover copper from nickel laterite leachusing resin with the iminodiacetate functional group. Resultsshow that when iron is Fe(II), copper recovery is higher thanwhen Fe(III) is present in solution [18]. is can occurbecause the iminodiacetate functional group has high af-�nity for Fe(III) [15, 42–44], once it was the highest metalrecovery among all in mg·L−1 in all pH studied.

Figure 5 shows results of metals recovery of Solution 2with Lewatit® TP 220, chelating resin with the bis-picolylamine functional group. At pH 0.50–2.00, chelatingresin was more selective for nickel than other metals in bothsolution, except for solution without the pre-reducingprocess at pH 0.50. At pH 2.50 and 3.00, in solution withthe pre-reducing process, cobalt was themetal more selectiveby the resin, followed by zinc and nickel. At pH 3.50,however, chelating resin was more selective for zinc, fol-lowed by nickel and cobalt. is phenomenon was also seenin Solution 1 experiments, where chelating resins selective

order changes for dierent pH values and also with the pre-reducing process. e dierence in the selective order forsolution with and without the reducing process can beexplained due to conversion of Fe(III) to Fe(II).

Chelating resin for Solution 2 with the pre-reducingprocess between pH 0.50 and 2.00 was more selective fornickel than cobalt and zinc. At pH 2.50 and 3.00, the resinwas more selective for cobalt, and at pH 3.50, chelating resinwas more selective for nickel and zinc, simultaneously.

e eect of pH for cobalt and zinc recovery fromSolution 3 by the bis-picolylamine resin is shown in Figure 6.Chelating resin has high selective for cobalt between pH 0.50and 2.00 in both situations. However, at pH 2.50 and 3.00,zinc was more selective by the resin than cobalt, and bothwere almost not recovered by the resin at pH 3.50. echange in the order of selectivity was also observed. Figure 7presents coe�cient distribution of copper, nickel, cobalt,and zinc in Solutions 1, 2, and 3 with the pre-reducingprocess.

It is possible seen that copper coe�cient distribution, inSolution 1, was maximum (186mL·g−1) at pH 2.00, in-dicating that the chelating resin Lewatit® TP 207 with theiminodiacetate functional group was more selective forcopper in this pH. In Solution 2, nickel coe�cient distri-bution was maximum at pH 3.50 (121mL·g−1); however, atthe same pH, zinc had higher coe�cient distribution(160mL·g−1) than nickel, indicating Lewatit® TP 220 withthe bis-picolylamine functional group was more selective forzinc than nickel. In the meantime, cobalt had higher co-e�cient distribution at pH 3.50 (61mL·g−1) than the otherpH values, which is seen in Figure 5, where copper recoverywas maximum at pH 3.5 as well as nickel and zinc. ForSolution 2, the chelating resin was more selective for nickelat pH 2.00 (43mL·g−1 for nickel and 15mL·g−1 for zinc andcobalt), where nickel recovery was 32.55% and zinc and

pH = 2.21 pH = 3.99

RCH2HN+

CH2COOH

CH2COOH

RCH2HN+

CH2COOH

CH2COO–

pH = 7.41

RCH2HN+

CH2COO–

CH2COO–

RCH2HN

CH2COO–

CH2COO–

pH = 12.3

Figure 3: Eect of pH in the iminodiacetate functional group [40].

Cu: solution 1Ni: solution 2

60 120 180 240 300 360 420 4800Time (min)

02468

101214

q (m

g of

ion.

g–1 o

f res

in)

Figure 2: Results of eect of time of Solution 1 and Solution 2.

4 International Journal of Chemical Engineering

cobalt, 14.86%. For Solution 3, cobalt coe�cient distributionwas maximum at pH 2.00 (198mL·g−1), being resin moreselective for this metal than others, and at pH 2.50, zinccoe�cient distribution was maximum (206mL·g−1).

Studies to recover metals from nickel laterite leach usingchelating resins indicated that resins with the iminodiacetatefunctional group are better to recover copper, while in orderto recover nickel and cobalt resins with bis-picolylamine arebetter [45, 46]. In experiments performed using Solution 1,Lewatit® TP 207 was more selective for copper, while ex-periments performed with Solutions 2 and 3 using Lewatit®

TP 220 cobalt and nickel were selectively recovered. Zincwas also selectively recovered depending on the pH value.

4. Conclusion

e aim of this work was to study the batch industrialprocess for metals recovery using two dierent chelatingresins from synthetic solution of nickel laterite leach. So-dium sul�te was used in order to reduce Fe(III) to Fe(II).Results indicated that Lewatit® TP 207 was more selectivefor copper than the other metals, due to its functional group,

CoNiZn

0.5 1 1.5 2 2.50pH

0%

10%

20%

30%

40%

Perc

enta

ge o

fad

sorp

tion

(a)

CoNiZn

0%

20%

40%

60%

80%

Perc

enta

ge o

fad

sorp

tion

0.5 1 1.5 2 2.5 3 3.5 40pH

(b)

Figure 5: Eect of pH in Solution 2 by the bis-picolylamine resin (a) without and (b) with the pre-reducing process.

CoZn

0.5 1 1.5 2 2.50pH

0%

10%

20%

30%

40%

Perc

enta

ge o

fad

sorp

tion

(a)

CoZn

0%

20%

40%

60%

80%

Perc

enta

ge o

fad

sorp

tion

0.5 1 1.5 2 2.5 3 3.5 40pH

(b)

Figure 6: Eect of pH in Solution 3 by the bis-picolylamine resin (a) without and (b) with the pre-reducing process.

CoCu

NiZn

0%10%20%30%40%50%60%

Perc

enta

ge o

fad

sorp

tion

0.5 1 1.5 2 2.50pH

(a)

CoCu

NiZn

0%

20%

40%

60%

80%

Perc

enta

ge o

fad

sorp

tion

0.5 1 1.5 2 2.5 3 3.5 40pH

(b)

Figure 4: Eect of pH in Solution 1 by iminodiacetate resin (a) without and (b) with the pre-reducing process.

International Journal of Chemical Engineering 5

and Lewatit® TP 220 was more selective for cobalt andnickel. Sodium sul�te increased metals recovery becausechelating resins were less selective for ferrous iron than ferriciron, and pH can be increased without ferric iron pre-cipitation, due to the fact that, while increasing pH, theconcentration of H+ decreases, as well as competition be-tween H+ and metals in solution for the functional group ofchelating resin. Another reason than can be explain themetals recovery raise is that ferrous iron occupies less activesites on the chelating resin than ferric iron. In all the so-lutions studied, metals recovery was higher after the pre-reducing process. A change in the selectivity order of resinswas observed comparing with and without the pre-reducingprocess, which may be caused by conversion of Fe(III) to Fe(III) and also by changing the pH. Pre-reducing processusing sodium dithionite and sodium metabisul�te wasstudied before, but the use of sodium sul�te as a cheap andsecure option can make the process economically viable andsecure. Industrial process can be a bene�t for the processinvolving chemical reducing and ion exchange process, inwhich metals recovery increases comparatively without thereducing process. Column experiments are the next step tosimulate �xed-bed reactors for the continuum process.

Data Availability

No data were used to support this study. Please feel com-fortable to contact the corresponding author if any doubtcomes up.

Conflicts of Interest

e authors declare that there are no con©icts of interestregarding the publication of this paper.

Acknowledgments

e authors acknowledge the São Paulo Research Foun-dation (FAPESP) (nos. 2012/51871-9, 2016/05527-5, and2017/06563–8) and CAPES for �nancial support. ey also

acknowledge the University of British Columbia and Uni-versity of São Paulo.

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Co: solution 1 with thepre-reducing processNi: solution 2 with thepre-reducing processCo: solution 3 with thepre-reducing process

Co: solution 2 with thepre-reducing processZn: solution 2 with thepre-reducing processZn: solution 3 with thepre-reducing process

050

100150200250

Kd (m

L·g–1

)

0.5 1 1.5 2 2.5 3 3.5 40pH

Figure 7: Coe�cient distribution of copper, nickel, cobalt, and zincwith the pre-reducing process.

6 International Journal of Chemical Engineering

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